TMS320F28335: F28335: eCAN - Receiving Remote Frames

Henrique T.

Part Number: TMS320F28335

In SPRUEU1 (2.9.1) is said that when a remote frame is received, the module compares the remote frame identifier to all identifiers of the mailboxes starting at the highest mailbox number in descending order. After finding a matching identifier in a send mailbox no further compare is done.

But for example if MB[25] and MB[20] both have an identifier equals to the Remote Frame Identifier, being MB[25] a receiver mailbox and MB[20] a send mailbox (with AAM=1), what will happen?

When the frame ID matches MB[25] the module continues comparing until MB[20]?

Just the RFP[25] will be set or both RFP[25] and RFP[20] will?

over 7 years ago

0 Hareesh Janakiraman over 7 years ago

TI__Guru* 95315 points

In the same section that you point to, the Reference guide says this:

With a matching identifier and the message object configured as receive mailbox, this message is handled like a data frame and the corresponding bit in the receive message pending (CANRMP) register is set. The CPU then has to decide how to handle this situation.

Does that answer your question?

0 Henrique T. over 7 years ago in reply to Hareesh Janakiraman

Intellectual 490 points

Not exactly... I understand what happens when the receive mailbox receives a remote frame... But to be simpler, my question is:

According to the text, the module scans the mailboxes starting at the highest mailbox number in descending order and stops when finding a matching identifier in a send mailbox. But will it continue to scan if it finds a matching identifier in a receiving mailbox?

Thanks for your attention

0 Hareesh Janakiraman over 7 years ago in reply to Henrique T.

TI__Guru* 95315 points

I have not tried this in silicon, but my interpretation of the spec suggests that once a matching ID is found, no further comparison would be made. I think the source of the confusion is the word "send" in "After finding a matching identifier in a send mailbox, no further compare is done", correct?

0 Henrique T. over 7 years ago in reply to Hareesh Janakiraman

Intellectual 490 points

Yeap, the word "send" is what raised me suspicious...

0 Hareesh Janakiraman over 7 years ago in reply to Henrique T.

TI__Guru* 95315 points

I tried this on silicon. On eCAN-B, I made MBX4 as Receive and MBX0 as Transmit (with AAM set), configured both with a STD ID ox 0x2. When I transmitted a Remote frame from eCAN-A with an ID of 0x2, it is received in MBX4 of eCAN-B and RFP4 is set. It is not received in MBX0.

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TMS320F28335: F28335: eCAN - Receiving Remote Frames